OpenAFS Master Repository branch, master, updated. BP-openafs-stable-1_8_x-359-g8b6ae28

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit 8b6ae2893b517bd4e008cae94acff70abe4d2227
Author: Andrew Deason <adeason@sinenomine.net>
Date:   Thu Mar 21 15:24:06 2019 -0500

    LINUX: Avoid lookup ENOENT on fatal signals
    
    Various Linux kernel operations on various Linux kernel versions can
    fail if the current process has a pending fatal signal (i.e. SIGKILL),
    including reads and writes to our local disk cache. Depending on what
    and when something fails because of this, some parts of libafs throw
    an ENOENT error, which may propagate up to callers, and be returned
    from afs_lookup(). Notably this can happen via some functions in
    src/dir/dir.c, and previously was possible with some code paths before
    they were fixed by commit 2aa4cb04 (afs: Stop abusing ENOENT).
    
    For the most part, the exact error given to the userspace caller
    doesn't matter, since the process will die as soon as we return to
    userspace. However, for ENOENT errors specifically for lookups, we
    interpret this to mean that the target filename is known to not exist,
    and so we create a negative dentry for that name, which is cached.
    Future lookups for that filename will then result in ENOENT before any
    AFS functions are called.
    
    The lingering abuses of the ENOENT error code should be removed from
    libafs entirely, but as an extra layer of safety, we can just avoid
    returning ENOENT from lookups if the current process has a pending
    fatal signal. So to do that, change all afs_lookup() callers in
    src/afs/LINUX to translate ENOENT to EINTR if we have a pending fatal
    signal. If fatal_signal_pending() is not available, then we don't do
    this translation.
    
    FIXES 134904
    
    Change-Id: I00f1516c2aa0f45f1129f5d5a44150b7539c31cc
    Reviewed-on: https://gerrit.openafs.org/13530
    Tested-by: BuildBot <buildbot@rampaginggeek.com>
    Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
    Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
    Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>

 src/afs/LINUX/osi_vnodeops.c |   13 +++++++++++++
 src/cf/linux-kernel-func.m4  |    3 +++
 2 files changed, 16 insertions(+), 0 deletions(-)

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